Magnetic tape unit

Abstract

The present invention relates to a magnetic tape unit to which a cartridge having a magnetic tape therein is detachably attached and which accesses a magnetic tape in accordance with an access request from a host. Software of the host which accesses a conventional magnetic tape unit to which a cartridge accommodating a plurality of cartridges is attached is used as it is while using the cartridge accommodating a large-capacity magnetic tape. Management information of a plurality of volumes is written in the cartridge, and a LOAD command from the host is replaced by a command for accessing an actual cartridge.

1 . A magnetic tape unit to which a cartridge accommodating a magnetic tape is detachably attached and which accesses the magnetic tape in accordance with an access request from a host, wherein 
 the cartridge accommodates the magnetic tape and includes a cartridge memory which stores information in a nonvolatile and rewritable manner,    the magnetic tape unit comprising:    a magnetic tape drive which accesses the magnetic tape;    a memory read/writer for accessing the cartridge memory; and    an access-controlling section which allows the cartridge memory to store management information of a plurality of volumes using the memory read/writer, and in which based on the management information, a LOAD command of the cartridge from the host is replaced by a command for accessing a region corresponding to a volume of a virtual cartridge which receives the LOAD command from the host in the magnetic tape accommodated in an actual cartridge loaded in this magnetic tape unit, the access-controlling section allowing the magnetic tape drive to access the magnetic tape accommodated in the actual cartridge.    
   
   
       2 . The magnetic tape unit according to  claim 1 , wherein the access-controlling section remains a state in which the magnetic tape is loaded in the actual cartridge in accordance with an UNLOAD command of the cartridge from the host, and the access-controlling section brings this state into a state in which the actual cartridge can be taken out in accordance with an EJECT command from the host.  
   
   
       3 . The magnetic tape unit according to  claim 1 , wherein the access-controlling section remains a state in which the magnetic tape is loaded in the actual cartridge until the number of UNLOAD commands from the host reaches a predetermined value, and the access-controlling section brings this state into a state in which the actual cartridge can be taken out if the number of UNLOAD commands from the host reaches the predetermined value.